The regular inspection of wooden structures such as utility poles, support pilings, and other timber structures is an essential part of the maintenance and upkeep of such structures. Aging wood can suffer from internal decay and/or rot as a result of insect and fungal infestations, as well as the presence of excessive moisture in the wood, and can develop voids, cracks, and cavities in its structure. Such flaws in the structural integrity of a utility pole or other wooden structure can lead to a loss of strength in the structure, decreasing the load that can be borne by the structure and in some cases necessitating restoration or even replacement. Therefore, accurate and repeatable methods of assessing the condition of wooden structures are required to minimize the risks associated with the aging of these structures.
The keys to utility pole inspection are identifying decay, measuring defects and estimating the percent remaining strength to determine whether the utility pole passes or fails the inspection, or requires remedial attention, such as supplemental wood preservative treatment, or reinforcement or restoration. Attempts to develop pole inspection instruments have not yet fully succeeded to add value or lower costs, and there is a need in the art for alternatives to the methods and devices that currently exist for the evaluation of utility poles.
Wood is a highly variable material and there are many possible decay patterns that are possible in any particular utility pole. These decay patterns also differ by the species of wood. The most accurate option for pole inspection remains a highly trained, professional inspector using time-proven procedures and tools. Some of these procedures include the following:
Visual inspection, or visual inspection combined with sound inspection procedures are typically suitable for identifying gross defects in utility poles that may be visible above the ground level. Using the visual inspection technique, trained personnel inspect the exterior of a utility pole or other wooden structure looking for structural deficiencies such as visible cracks, fissures, and splits in the surface of the structure, plant life or algae growing on the wood, and holes bored by woodpeckers or insects. Visual inspection, alone, can be suitable for identifying gross defects visible in a wooden structure, but can produce variable results that depend on the experience and the diligence of the particular inspector.
Sound and bore procedures allow an inspector to bore inspection holes after hammer sounding identifies areas where decay may exist in a utility pole. A shell thickness indicator may also be used to measure internal decay. For example, “sound and prod” and “sound and bore” techniques involve inspection personnel “sounding” the structure by striking it with a hammer, spike, or other instrument and listening to the resulting sound for hollow-sounding noises or other audible indications of internal deficiencies. The inspection personnel next may engage in “prodding” or “probing” the pole by inserting a screwdriver, drill, or other boring tool to sample the interior of the pole or other structure in a search for decay or damage. Personnel may also scrape the exterior of the wood to look for surface decay.
Partial excavation plus sound and bore procedures allow an inspector to access a portion of the pole below ground. These procedures are useful for the identification of external decay and termites. Excavation to a depth of 18 inches to 24 inches plus sound and bore techniques allow the most complete access to the decay-prone region of poles, where moisture and oxygen encourage decay.
Electronic inspection devices are instruments that typically depend on theories, such as frequency or time of flight of a sonic wave, or physical characteristics such as hardness of wood to identify anomalies in a utility pole. For example, the Shigometer can identify early stages of decay, but it is not a pass/fail device. Other non-invasive or minimally-invasive inspection methods use equipment such as the Resistograph®, which measures the energy required to maintain a constant drilling speed in a wooden structure, or the Pilodyn penetrometer, which measures the depth into which a pre-loaded spring forces a pin into the surface of a wooden structure.
There remains a need in the art for alternative minimally-invasive techniques to complement existing techniques for the inspection of utility poles and other wooden structures, particularly for the detection of incipient decay and external decay below ground without excavation. The devices, systems, and methods of the present invention are designed to meet this and other needs.